The use of interconnected steering arms to control the position of wheel sets in a radially steerable railway car truck is a well established technique. Basically, this technique utilizes the nature of the conical wheel tread along with the shape of the rail in order to develop a radial steering function as the truck moves through curves and also to provide lateral stability when moving on straight track.
Because several types of brake rigging or brake actuating apparatus are presently and have in the past been utilized in the railroad industry, this can present considerable difficulty when retrofitting an existing truck with a radial steering arm assembly. Some of the brake riggings have elements of their mechanism disposed through the truck bolster and likewise some of the prior steering arm assemblies also utilize elements which pass through openings in the truck bolster. Because of these configurations, mechanical interferences between the brake rigging and the steering arms can significantly limit the application of steering arm designs which pass through the truck bolster.
One additional complication of steering arm assemblies which pass through the bolster is due to the existing passageway through the bolster being located in an off-center position relative to the center line of the truck. Because of this bolster configuration, the steering arms are not identical and must be constructed in pairs. These pairs of steering arms must be correctly matched to assure that the truck axles will position the wheels in a square configuration when the truck is assembled.